As a conventionally stent structure, a stent shown in FIG. 7 (a structure described in FIG. 1 of Patent Documents 1 and 2) has been known. In the stent described in Patent Documents 1 and 2, a plurality of cells 11 have been connected with each other in the circumferential direction to be arranged so that the central axis C1 of the stent 15 is surrounded to constitute a ring unit 12. Each of the opposing cells 11 and 11′ of the adjacent ring units 12 and 12′, respectively, is bridged by a connecting element 14 having an approximately or substantially S shape.
Moreover, as other stent structures, structures shown in FIGS. 3 and 5 (structures described in FIGS. 1 and 3 of Patent Document 3) have been known. These stents include a first ring unit 8 comprising a first cell group in which a plurality of first cells 7 are connected with each other in the circumferential direction and a second ring unit 8′ comprising a second cell group in which a plurality of second cell 7′ are connected with each other in the circumferential direction so that the first and second ring units are alternatively arranged to surround the central axis C1 of the stent 6. The first and second cells in the adjacent first and second ring units 8 and 8′, respectively, are disposed oppositely and some (not all) of the first and second cells are bridged by a connecting element 9. The shapes of the first and second cells 7 and 7′ are axisymmetrical of the stent 6 about the connecting element 9. The cell with a bridged part formed of the above-mentioned connecting element 9 is slightly longer than the cells which are not bridged with each other.
Furthermore, referring to a stent 1 (S-Stent) shown in FIG. 8 which is produced and available from another company, cells 16 and 16′ are partially bridged by the connecting element 17 and have a constant length. The connecting element 17 is about 0.2 mm in length. In a stent 2 (Driver) shown in FIG. 9 which is produced and available from another company, cells 18 and 18′ are formed from CoCr alloy wire which is bent in the shape of zigzag, and some of the oppositely disposed cells are bridged by a connecting element 19 through welding.